The present invention relates to a hydraulic damper for use in a vehicle such as an automobile, and more particularly relates to a hydraulic damper which is provided with a bump stopper.
A hydraulic damper provided with a spring seat and a bump stopper is known in the field as a hydraulic damper that may be used in the front suspension of a vehicle. The spring seat is adapted to support the lower end of a suspension spring. It is necessary to prevent the chassis of the vehicle from directly colliding with the upper end portion of the hydraulic damper to prevent damage thereto when the damper is contracted during running of the vehicle. To this end, a bump rubber is mounted on the chassis of the vehicle and a bump stopper is mounted on the upper end of the hydraulic damper. The bump rubber is stopped and compressed by the bump stopper and is deformed when the hydraulic damper is contracted, so that the bump rubber absorb the impact energy and the hydraulic damper can thus be prevented from being damaged.
Shown in FIG. 1 is an example of such type of hydraulic damper. An outer tube 102 of a cylinder of a hydraulic damper 101 is provided with a plurality of projecting portions 106 including first and second stepped portions 106a and 106b, respectively. A spring seat 107 is secured to the outer tube 102 with an inner diameter portion 107a of the spring seat 107 being press-fitted on the first stepped portion 106a of the outer tube 106 and with a lower stepped portion 107b of the spring seat 107 being engaged with the second stepped portion 106b of the outer tube 106. A packing cap 103 is secured to the upper end of the outer tube 102 by welding and a bump cap 104, in turn, is welded on the packing cap 103. A plate cap 108 provided with a bump plate 105 welded thereon is press-fitted on the outer periphery of the bump cap 104. Thus, a bump stopper 110, which consists of the bump cap 104, plate cap 108 and bump plate 105, is secured to the upper end of the outer tube 102. Numeral 109 designates a piston rod which is connected to a piston (not shown) movably received in the cylinder and which extends to the outside of the cylinder.
With such a conventional hydraulic damper, it is very difficult for the spring seat 107 to be fixedly secured to the outer tube 102 by such means as welding in an automatic assembly line because of its large dimensions. Therefore, the spring seat 107 is, press-fitted on the outer tube 102 after the assembly of the other parts has been completed. On the other hand, as described above, a bump rubber (not shown) mounted on the chassis of a vehicle (not shown) is stopped or abutted and compressed by the bump stopper 110 so as to be deformed radially of the bump plate 105 when the hydraulic damper 101 is contracted. If the bump rubber is deformed beyond the outer periphery of the bump plate 105, the bump rubber pressed by the chassis from the above is subjected to shearing force by the edge of the outer periphery of the bump plate 105. With such shearing force being applied repeatedly, the bump rubber gradually deteriorates. To avoid this problem, it is necessary for the bump plate 105 to have a large area so that the bump rubber is not deformed beyond the outer periphery of the bump plate 105 when it is compressed. Therefore, the outside diameter of the bump plate 105 is usually made larger than the outside diameter of the outer tube 102 or the inside diameter of the spring seat 107. In an assembly operation, therefore, assembly of other parts is completed first, the spring seat 107 is next press-fitted on the outer tube 102 and the plate cap 108 is finally press-fitted on the bump cap 104.
In such a conventional hydraulic damper, the plate cap 108 provided with the bump plate 105 welded thereon is merely press-fitted on the bump cap 104, so that only the frictional resistance generated between the bump cap 104 and the plate cap 108 acts to prevent the plate cap 108 from being upwardly disengaged from the bump cap 104. This frictional resistance is not necessarily sufficient for completely preventing such disengagement and it is possible that the plate cap 108 may come out of engagement with the bump cap 104 as a result of vibration or shock applied to the damper during transportation of the damper or of poor treatment of the damper.